This application relates to the art of locking devices and, more particularly, to locking devices for selectively locking a movable member against movement in at least one direction. The invention is particularly applicable for use in fluid operated braking systems for vehicles and will be particularly described with reference thereto. However, it will be appreciated that the improved locking device of the present invention has broader aspects and may be used for selectively locking movable members against movement in mechanisms other than vehicle brakes.
Pneumatically operated vehicle brakes have air motors to which pressurized air is supplied for applying the vehicle brakes. Systems of this type also include a parking brake arrangement wherein pressurized air is directly connected to the air motors from a reservoir for applying the brakes. In parking brake arrangements of this type, a slow leak or other failure in the pressurized air source may cause release of the brakes, and this presents a very hazardous condition.
It is known to have mechanical locking devices for locking the parking brakes against release in the event of a failure in the pressurized air source. In one arrangement of this type, the reciprocating rod brake actuator must be replaced with a special toothed rod. In another arrangement, the conventional clevis connecting the rod to the brake adjuster must be replaced with a special straight travel clevis. Arrangements of this type are relatively expensive and require substantial installation time.
It would be desirable to have a locking device of the type described which would not require replacement of existing brake parts with special new parts.